Filter circuits



Oct. 19,1926. 1,603,805

H. RIEGGER FILTER CIRCUITS Filed August a, 1922 Patented Oct. 19, 1926.

UNITED STATES PATENT OFFICE,

HANS RIEGGER, OF IBERLIN-PANKOW, .GERM ANY, ASSIGNOR 'I'O SIEMENS .8:HELSKE,

AKTIENGESELLSOHAFT, OF SIEMENSSTADT,

CORPORATION.

NEAR BERLIN, GERMANY, A GERMAN FILTER cracurrs.

Application filed August 8, 1922, Serial No. 580, 69, and in GermanyAugust 17, 1921.

It is known to use for. the transmission of electric oscillations achain of filter circ u1ts which permit the passage of oscillationswithin a determined frequency range, but which suppress the oscillatorycurrents out*.

tive as well as capacitative coupling exists,

the self-induction and capacity at the points of coupling'being soselected that at the limits of the filter range the coupling becomeszero.

A chain of filter circuits of this type has the advantage that at theabove-mentioned limits practically no oscillations are transmittedwhereby the admittance of the chain beyond these limits is generallyquite small while all frequencies located within these limits are welltransmitted.

An embodiment of the present invention is shown by way of example on theaccompanying drawing, in whic 2 Figure 1 is a diagrammaticalillustration of the filter circuit chain, while Figure 2 shows theeficiency curve, and

Figure 3 shows a modification of the circuits shown in Figure 1.

The windings 1 at one end of the chain, being suitably excited transmitthe oscillations through the chain of filter circuits to windings 2 atthe other end of the, chain, by which latter windings they may be transmitted to any desired receiving element. The

chain consists of two members 3 and 4:. Both members are of almostsimilar construction. The member 3, for instance, consists of twoelementary oscillatory circuits of which one comprises theself-induction 5 and the capacity 6,while the other comprises theselfinduction 7 and the capacity 8. These two elementary circuits arecoupled with each other inductively by the transformer windings 9 and 10and capacitatively by the condenser 11,-and each of these elementarygircuits is tuned to a frequency to be transmitted to produce a wellknown two peak resonance curve. The windings 12 serve as a medium forcoupling this chain member to the energy supply coil 1, and the windings13 serve as a coupling medium with the second chain member 4. If theself-induction produced by 9 and 10 and the capacity 11 form forthemselves a combination in resonance with the transmitted electricoscillations, the

resonance occurs at one of the two limits of the desired frequenc range,beyond which oscillatory currents s ould not be allowed to pass. In thesecond chain member 4, on'the other hand, the corresponding parts are sodimensioned that the resonance occurs at the other limit of the range.In this manner, an efficiency is produced as is illustrated by the curveshown in Figure 2.

The electromotive force in the supply windings 1 (Figure '1) may bemaintained constant, the frequency of oscillations being howevervariable. If in. this case the frequencies are plotted as abscissaewhile the currents that are produced in the receiving wlndin s 2 areplotted as ordinates, the curve s own in Figure 2 will be produced. Itis assumed in this case that the two systems are suitably coupled so asto slightly broaden the resonance curve within a very narrow band offrequencies, which is deslrablc in practice. For this reason theresonance curve shown in Figure 2 has been shown with well known twopeaks closely located together, which represents for all practicalpurposes a resonance curve with a slightly broadened average peak havingsubstantially the same maximum value between the frequencies (.0 and Atthe frequency w, resonance occurs at the coupling points a, b in chainmember 3, and at the frequency (0 resonance occurs in the chain member 4at the corresponding points. Consequently, no currents How in thewindings 2 at the frequency w, or (0 Within the frequency thefrequencies o, and w The resonance curve must also at these frequenciestouch the abscissae line and it will, therefore, not considerably ascendbetween (0 and w, on the one hand and between 1, and w, on the otherhand.

Such a modification is shown inFigure 3. Aside from the coupled members'3 and 4, such as are shown in Figure 1 the chain further contains thecoupled members 23 and 24. The con lings between the points a and b inthe mem er 3 becomes substantially zero value at the vfrequency w, (Fi're 2),

between the points a and d in mcm er 4 it becomes zero at the frequency(0 both similar to the manner explained with reference 1 each member,consisting of a plurality of elementary oscillating circuitselectromagtnetically and electrostatically coupled with each other, theself-induction and the capacity at the coupling points being suitablyselected to reduce the degree of couplingat a predetermined frequency tosubstantially zero value.

2; An improved chain of electric filter circuits, comprising a pluralityof members each member consisting of a plurality of elementaryoscillating circuits electromagnetically and electrostatically coupledwith each other, the self-induction andthe capacity at the couplingoints being suitably selected to reduce the egrce of coupling at apredetermined frequency to substantially zero value, one member of thechain having said zero value at the lower limit, and another memberhaving said zero value at the upper limit of a predetermined range offrequencies.

In testimony whereof I afiix my *si ature.

HANS RIEG ER.

